Clarksville weekly chronicle. (Clarksville, Tenn.) 1873-1890, 1887-03-19
PHOTOTYPIC WORK.
SOMETHING ABOUT THE VARIOUS
PROCESSES NOW EMPLOYED.

Tho Methods Of Goupii, In Paris--Quicl-
ness of American Processes-The Ac-
tion OF Light on sensitized GeIatine.
PhOtogravure.
TIE most common forms Of reproductive
art nowadays are those based on photog-
raphy, and IL may not be generally known
that the most extensive concern In the
country that Is devoted to this kind of
work is housed In Brooklyn. The COM
pany who controls these works and give
employment to q considerable number Of
operatives, some of whom are to be re-
garded as artists rather than mechanics,
for into the finishing and printing of the
plates taste as well as skill must enter.
The house of Goupil, In Paris, has until
recent years enjoyed almost monopoly
of photogravure, and its work has celeb
rity for strength and clearness The
Goupl process Is q secret, but 1t is evil
dent from the length of time taken to
prepare plato, and from the appearance
OF sundry lines and markings that would
not commonly show in q solar print, that
hand work is nearly as important fac
tor as chemical evolution. The company
here in Brooklyn finishes a plate in as
many hours as days are taken by the
Goupil firm, and the results are In many
instances surprising. Advances in the
art are still 10 be made, but there is u
broad foundation TO work upward from.
There are dozens Of names for what Is
substantially the same process-the photo
type, photoprint, mosstype, albertype,
artotype, hchtdruk, heliotype, carbon
print, autoglyph, Ives process, Nielsen
bach process, photo Autograph, photo
caustic print, photo gelatine print, photo
engraving, zinc etching and photogra'
vure. The action Of light on sensitized
I gelatine or other material is the occasion
of all these FORMS Gelatine is made sen
sitive by treatment with bichromate Of
potash, which likewise renders It insol
uble by water, and in this condition Il
win stake grease, when that is applied
but when a gelatine sheet is placed under
Photographic negative the effect of ligh
striking through the glass is to close tn,
pores of the gelatine and harden it, ant
where light does not act the gelatine be
comes soft and absorbent. After tn,
sheet has received the impress from tn,
negative q greasy ink will adhere to tn,
hard portions, while the sponge areas
being kept moist with water, refuse 1t
You apply your ink, lay piece of pape
on 1t, stamp 1t, the ink comes off on tn
paper and there is your picture-a hello
type, in commercial phrase.
APPLIED TO STONE PRINTING.
This process is much the same as 18th
ography, but the photographic stone hold
grease only where there are decided lines
while gelatine receives the impress of
hundred gradations of light and shade
Photography is applied to stone printing
where anything is to be represented b.
clean masses of black and white, and it i
therefore useful for copying maps, plans
: tracings, ink drawings, designs, miniatur
calendars, papers and catalogues, line en-
cravings, autograph letters, and so on
In that case paper coated with gelatine |
printed on by o negative, as in the case
Of an ordinary photograph, and the greas
taking lines are transferred bodily to tn
stone. When the ink lines are transferre
; to zinc instead of stone and the expose
portions of the metal are eaten down b
acid, leaving the lines in relief, plate
made that is similar to stereotype, an
this form is commonly used for cheap Il
Illustrations in daily papers. A plaste
cast may be taken from q gelatine im
press after the lines have set, and fror
/ this may be made metal plate that wi
| print what are called photo engravings.
. For photogravure bichromatized gelf
. tine is mixed with sand or emery dust, tn
/ picture is thrown on it from negative
, the grease taking lines harden, the ligh
!. portions are swollen with water and
! copper shell is deposited ON it as an electro
type. The sand gives grain to the SUI
e face and holds the ink where 1t is desil
! able to impart half tint. In the hand
!, of a skillful printer proof photograph
9 can be made almost as strong as an etcf
: ing, as it is easy to wipe out the hig
lights until they are represented by tn
q actual whiteness of the paper that rt
ceives the print, while tones and masse
q of shadow are obtainable by leaving film
! of ink of less or greater density on til
= metal surface. Brooklyn Eagle.